tc-init-health-check-listener

Tomcat Initialization Health Check Lifecycle Listener

Why

There is no easy way to check from a shell script if all Tomcat components (i.e.: Server, Service(s), Connector(s), Executor(s), Container and Context(s)) initialized properly during startup.

How

This lifecycle listener waits for a Lifecycle.AFTER_START_EVENT from the Server component. When received, the LifeCycleState of each Tomcat component is checked.

Optionally, it is possible to notify an external process (e.g.: the startup script) via a FIFO or with a UDP packet and/or trigger a server shutdown upon failure.

Version

This version (8.0.32) was built and tested against Tomcat 8.0.32, but should work with newer versions as well.

Build

git clone https://github.com/goldendeal/tc-init-health-check-listener.git
cd tc-init-health-check-listener
mvn package

Maven

<dependency>
  <groupId>gr.xe</groupId>
  <artifactId>tc-init-health-check-listener</artifactId>
  <version>8.0.32</version>
  <packaging>jar</packaging>
</dependency>

Install

Copy tc-init-health-check-listener/target/tc-init-health-check-listener-<version>.jar to ${CATALINA_HOME}/lib or ${CATALINA_BASE}/lib

Usage

In your server.xml add a server lifecycle listener:

<?xml version='1.0' encoding='utf-8'?>
<Server port="8005">
  <Listener className="gr.xe.dc.tomcat.listeners.InitHealthCheckListener"/>
  ...
</Server>

Available Attributes

Attribute	Type	Default Value	Description
shutdownOnFailure	boolean	true	Trigger server shutdown on failure
notifyFIFO	String	none	A FIFO where the initialization status will be written
notifyAddress	String	localhost	Destination address of the UDP packet containing the initialization status
notifyPort	Integer	Same as Server shutdown port	Destination port of the UDP packet containing the initialization status

Shell usage

The following have been tested with bash.

FIFO

If using notifyFIFO:

read -t <timeout> STATUS <> /path/to/FIFO

if [ $? -ne 0 ]; then
  echo "Timed out"
  exit 1
fi

if [ "${STATUS}" -eq 0 ]; then
  echo "Success"
  exit 0
else
  echo "Failure"
  exit 1
fi

UDP

If using notifyAddress and notifyPort:

STATUS=$(timeout <timeout> socat UDP-RECVFROM:<notify port> STDOUT)

if [ $? -ne 0 ]; then
  echo "Timed out"
  exit 1
fi

if [ "${STATUS}" -eq 0 ]; then
  echo "Success"
  exit 0
else
  echo "Failure"
  exit 1
fi